Effect of operating conditions on melt rheological characteristics during twin-screw food extrusion

Data on operating (feed rate, feed moisture content, screw speed, and tempe rature) and process variables (product/barrel/die temperatures, zone 4-5/di e pressures, total power consumption) of a co-rotating twin-screw food extr uder, and extrudate moisture content were collected at 0.5 s intervals. The steady-state data were analyzed and the mean residence time and average ap parent viscosity of melted cornmeal determined. The average apparent viscos ity was calculated by using the total power consumption method and modeled as a function of the operating variables. The addition of two extra reverse paddles to the screw (configuration B) caused a decrease in fluid consiste ncy coefficient (16.865 vs 20.130 kPa.s(n)) and an increase in shear-thinni ng behavior (0.22 vs 0.44) of the melt.